Hi Cameron,
Thanks for answer. The problem with such approach is that within GQueues I do not see the true deadline for the task.
On the list I see the task with date in red which suggest it's overdue, it also comes up before the real deadline when filtering in Smart Queues.
However not to change whole logic of the app maybe for the tasks with set duration you could consider
only displaying the end date after the start date in brackets? (as an option which can be switch on and off in Settings, if someone doesn't need this).
Something like this:

This, I believe, relatively simple change (only with the way information is presented, no change to the app logic) would allow to see immediately than like in the above example - the task should start on May 22nd last 3 days and be finished on May 24th, directly on the list, without opening the date/time dialog box (so I have it on the radar screen but I see the real due date).
I'm convinced that would help a lot to all of us who struggle with lack of separate start and end date. I hope you can consider such suggestion.
Best
Piotr